使用后退按钮从片段返回到主活动

Question

嗨，我已经在应用程序抽屉中创建了片段，现在当我按下一个片段上的后退按钮时，它正在关闭应用程序。

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (event.getAction() == KeyEvent.ACTION_DOWN) {
        switch (keyCode) {
            case KeyEvent.KEYCODE_BACK:
                if (myWebView.canGoBack()) {
                    myWebView.goBack();
                } else {
                    finish();
                }
                return true;
        }
    }
    return super.onKeyDown(keyCode, event);

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }

if (fragment != null) {
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_main, fragment);
        ft.addToBackStack("close");
        ft.commit();




    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);

Answer 1

当您将片段添加到某个容器或使用xml对其进行膨胀时，它不会添加到backstack中，因此，当“On Backpressed”发生时，它会从backstack中抛出最后一个活动--这是承载片段并因此退出应用程序的活动。我想这篇文章：Android：碎片背栈

可以帮助您，它解释了如何将片段事务添加到backstack中：

FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.replace(..............);
    fragmentTransaction.addToBackStack("fragment transaction name, not required");
    fragmentTransaction.commit();